In a comment on r/ultralight, fancy outdoorsman Dan Durston links to the following paper in The Journal of the Textile Institute which supposedly shows that at a given high dose of UV radiation nylon was reduced to 15% of its original strength whereas polyester remained above 99%:
https://www.tandfonline.com/doi/abs/10.1080/00405000.2013.796629
As much as I’d like to read the paper for myself, at $50 a pop I’ll take Dan’s word for it. When I was out tent shopping it became very clear that one advantage of polyester over nylon was that nylon sags when wet and polyester doesn’t, something I can personally vouch for based on an entire season in my Lunar Solo. I had no idea, however, about just how differently the two materials degrade in the outdoors. Definitely something to keep in mind for future purchases.